OS1-OS3 is very casual raid content, and with current item levels it's not required to have materia since beating enrage timers is not an issue in any way. People are also running the content on alts and may not want to fully meld several jobs. I would expect melds in OS4 and Ultimate at this point, but for anything else I don't care (I do meld my own gear for the jobs I use, but have been running OS1-OS3 and Shinryu ex without melds too when just testing how it feels to raid on particular job).